hydroboration and hydrocyanation of olefin 3.ppt

Hydrogenation and hydrocarbon

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2. Hydroboration and Hydrocyanation of
Olefins
Dr Tahir Mahmood
Associate Professor of Chemistry

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Hydroboration
Hydroboration reaction was introduced by H. C. Brown in
1959.
Hydroboration is synaddition of boranereagent H-BR
2to
alkenes.

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Other borane reagents

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Mechanism of Hydroboration:

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Metal-Catalysed hydroboration:
Männing and Nörth introduced metal catalyzed
hydroboration reaction in 1985.
The complex RhCl(PPh
3)
3(also known as Wilkinson’s
catalyst) became the first highly active catalyst for
hydrobortion
Wilkinson’s catalyst

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Mechanism

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Synthetic applications of Hydroboration

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HydrocyanationistheprocessinwhichHCNisaddedacrossa
doublebondofanalkenetoformanitrile

Hydrocyanation
Thisreactionmaybeusedtosynthesizenitriles
fromalkenesoralkynesinaMarkovnikovor
anti-Markovnikovfashion.

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Catalysed Hydrocyanation is of two types
Nickel-catalyzed hydrocyanation
Copper-catalyzed hydrocyanation

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Nickel-catalyzed hydrocyanation

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Atelevatedtemperatureterminalalkenesmaybe
hydrocyanatedbyNicomplexinthepresenceofaLewisacid
andprovideanti-markovnikovadditionselectively.

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Catalyst decomposition
Deactivationcantakeplaceiftheintermediate
hydrideoralkylspeciesreactwithHCN
.

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Hydrocyanation of 1,3 Butadiene
DuPont has commercialisedthe addition of HCN to
butadiene for the production of adiponitrile[ADN,
NC(CH
2)
4CN], a precursor to 6,6-nylon.

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Isomerization of 2M3BN to 3PN

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Copper-catalyzed hydrocyanation
Copper is a good catalyst for hydrocyanation reaction
of alkenes as compared to nickel complex..
Copper catalysis appears to be a very convenient and
efficient method for realizing the
monohydrocyanation of butadiene, as the yields are
good and the reaction leads selectively to substituted
2-butenes.
95%

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Synthetic Applications of Nitriles

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